Interference control between different radio communication systems involving user equipments

ABSTRACT

A first User Equipment (UE), a second UE, a first Radio Network Node (RNN), and methods therein for controlling interference between transmissions in a first system and transmissions in a second system. The first system comprises the first UE and the first RNN serving the first UE. The second system comprises the second UE and a second RNN serving the second UE. The first system has a first priority in a first part of a shared spectrum and the second system has a second priority in the first part of the shared spectrum, wherein the first priority is higher than the second priority. The method in the first UE comprises transmitting a signal to a second RNN that is to perform a downlink transmission to the second UE, which signal is configured to control the transmission of the second RNN.

TECHNICAL FIELD

Embodiments herein relate to a first user equipment, a second userequipment and a first radio network node, as well as to methods therein.In particular, embodiments herein relate to the control of interferencebetween transmissions in a first radio communications system and asecond radio communications system.

BACKGROUND

Communication devices such as User Equipments (UE) are enabled tocommunicate wirelessly in a radio communications system, sometimes alsoreferred to as a radio communications network, a mobile communicationsystem, a wireless communications network, a wireless communicationsystem, a cellular radio system or a cellular system. The communicationmay be performed e.g. between two user equipments, between a userequipment and a regular telephone and/or between a user equipment and aserver via a Radio Access Network (RAN) and possibly one or more corenetworks, comprised within the wireless communications network.

User equipments are also known as e.g. mobile terminals, wirelessterminals and/or mobile stations, mobile telephones, cellulartelephones, or laptops with wireless capability, just to mention someexamples. The user equipments in the present context may be, forexample, portable, pocket-storable, hand-held, computer-comprised, orvehicle-mounted mobile devices, enabled to communicate voice and/ordata, via the RAN, with another entity.

The wireless communications network covers a geographical area which isdivided into cell areas, wherein each cell area being served by anetwork node such as a Base Station (BS), e.g. a Radio Base Station(RBS), which sometimes may be referred to as e.g. eNB, eNodeB, NodeB, Bnode, or BTS (Base Transceiver Station), depending on the technology andterminology used. The base stations may be of different classes such ase.g. macro eNodeB, home eNodeB or pico base station, based ontransmission power and thereby also cell size. A cell is thegeographical area where radio coverage is provided by the base stationat a base station site. One base station, situated on the base stationsite, may serve one or several cells. Further, each base station maysupport one or several radio access and communication technologies. Thebase stations communicate over the radio interface operating on radiofrequencies with the user equipments within range of the base stations.

In some RANs, several base stations may be connected, e.g. by landlinesor microwave, to a radio network controller, e.g. a Radio NetworkController (RNC) in Universal Mobile Telecommunications System (UMTS),and/or to each other. The radio network controller, also sometimestermed a Base Station Controller (BSC) e.g. in GSM, may supervise andcoordinate various activities of the plural base stations connectedthereto. GSM is an abbreviation for Global System for MobileCommunications (originally: Groupe Spécial Mobile).

In the context of this disclosure, the expression Downlink (DL) is usedfor the transmission path from the base station to the mobile station.The expression Uplink (UL) is used for the transmission path in theopposite direction i.e. from the mobile station to the base station.

In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE),base stations, which may be referred to as eNodeBs or even eNBs, may bedirectly connected to one or more core networks.

UMTS is a third generation mobile communication system, which evolvedfrom the GSM, and is intended to provide improved mobile communicationservices based on Wideband Code Division Multiple Access (WCDMA) accesstechnology. UMTS Terrestrial Radio Access Network (UTRAN) is essentiallya radio access network using wideband code division multiple access foruser equipments. The 3GPP has undertaken to evolve further the UTRAN andGSM based radio access network technologies.

According to 3GPP/GERAN, a user equipment has a multi-slot class, whichdetermines the maximum transfer rate in the uplink and downlinkdirection. GERAN is an abbreviation for GSM EDGE Radio Access Network.EDGE is further an abbreviation for Enhanced Data rates for GSMEvolution.

Current radio communication systems are operating in so-called licensedspectrum implying that within a specific geographical region, forexample a country, a certain range of frequencies is assigned to asingle operator for exclusive usage.

In contrast, current wireless-Local Area Network (LAN) technologies areoperating in so-called unlicensed spectrum. Within such an unlicensedspectrum, anyone is allowed to operate transmitter equipments as long asthe transmission conforms to some basic requirements, such asconstraints on transmit power and transmitter out-of-band emissions.Thus, within a certain geographical region there may be multiplewireless-LAN operators, operating essentially independent of each other,on the same frequency.

Operation in licensed spectrum allows for good control of theinterference to which transmissions may be subject. Thus, operation inlicensed spectrum allows for high-quality wireless communication even incase of relatively-high-traffic-load situations.

At the same time, in a multi-operator scenario the use of licensedspectrum leads to spectrum fragmentation as the total available spectrumhas to be divided into disjoint parts, where each spectrum part islicensed to, and exclusively used by, a certain operator. In alow-traffic-load situation, a substantial part of the spectrum may thenlocally and instantaneously be unused as, at a certain time, one orseveral operators may have no active users what-so-ever within a certainarea. If that spectrum could be used by other operator(s) the data ratesthat could instantaneously be offered by an operator may be increased,leading to an overall improved spectrum utilization. However, withconventional spectrum licensing, where each spectrum part is assignedto, and exclusively used by, a single operator, this is not possible.

For operation in unlicensed spectrum the situation is essentially theopposite. In high-traffic-load situations the use of unlicensed spectrummay lead to more unpredictable interference, difficulties to providegood quality-of-service, and, in general, degraded spectrum efficiency.In low-traffic-load situations the use of unlicensed spectrum, where theoverall available spectrum is available to every operator, may allow forhigher per-operator bandwidth availability, corresponding possibilitiesfor higher data rates, and overall improved spectrum utilization.

In the scientific paper “A dynamic spectrum allocation between networkoperators with priority-based sharing and negotiation” (2005 IEEE16^(th) International Symposium on personal, indoor and mobile radiocommunications, 978-3-8007-2909-8105, pages 1004-1008), a spectrumsharing algorithm is disclosed. In the spectrum sharing algorithm thepriority between network operators and the priorities of multiple classservices are incorporated into the spectrum sharing metric, while alsoaccommodating the urgent bandwidth request by proposing a negotiationprocedure. The proposed scheme allocates the spectrum dynamically,reflecting the long-term occupation ratio between the network operatorsand the priorities of multiclass services.

A drawback with prior art systems is that it is not possible to combinehigh robustness at high traffic load (where the use of dedicatedspectrum is preferred) with high spectrum efficiency at low traffic load(where flexible spectrum sharing is preferred). The method in the paperreferred to above partly addresses this drawback but is, due to theslowness of the method, only able to adapt to long-term occupation ofthe spectrum and is thus not able to provide good efficiency at lowtraffic load when the instantaneous traffic demands are varying rapidly.

SUMMARY

An object of embodiments herein is to provide a way of improving theperformance in a communications network.

According to a first aspect of embodiments herein, the object isachieved by a method in a first user equipment for controllinginterference between transmissions in a first radio communicationssystem and transmissions in a second radio communications system. Thefirst radio communications system comprises the first user equipment anda first radio network node serving the first user equipment. The secondradio communications system comprises a second user equipment and asecond radio network node serving the second user equipment. The firstradio communications system has a first priority in a first part of ashared radio spectrum and the second radio communications system has asecond priority in the first part of the shared radio spectrum, whereinthe first priority is higher than the second priority.

The first user equipment transmits a signal to a second radio networknode that is to perform a downlink transmission to the second userequipment, which signal is configured to control the transmission of thesecond radio network node.

According to a second aspect of embodiments herein, the object isachieved by a first user equipment for controlling interference betweentransmissions in a first radio communications system comprising thefirst user equipment and a first radio network node serving the firstuser equipment, and transmissions in a second radio communicationssystem comprising a second user equipment and a second radio networknode serving the second user equipment. The first radio communicationssystem has a first priority in a first part of a shared radio spectrumand the second radio communications system has a second priority in thefirst part of the shared radio spectrum, wherein the first priority ishigher than the second priority.

The first user equipment comprises a transmitting circuit configured totransmit a signal to a second radio network node that is to perform adownlink transmission to the second user equipment, which signal isconfigured to control the transmission of the second radio network node.

Since the signal is transmitted from the first user equipment to thesecond radio network node, the transmission of the second radio networknode is controlled, whereby interference from the second base station tothe first user equipment is avoided or at least reduced. This results inan improved performance in the communications network.

According to a third aspect of embodiments herein, the object isachieved by a method in a second user equipment for controllinginterference between transmissions in a first radio communicationssystem comprising a first user equipment and a first radio network nodeserving the first user equipment, and transmissions in a second radiocommunications system comprising a second user equipment and a secondradio network node serving the second user equipment. The first radiocommunications system has a first priority in a first part of a sharedradio spectrum and the second radio communications system has a secondpriority in the first part of the shared radio spectrum, wherein thefirst priority is higher than the second priority.

The second user equipment receives a signal from the first radio networknode, which signal is configured to control a transmission of the seconduser equipment.

According to a fourth aspect of embodiments herein, the object isachieved by a second user equipment for controlling interference betweentransmissions in a first radio communications system comprising a firstuser equipment and a first radio network node serving the first userequipment, and transmissions in a second radio communications systemcomprising a second user equipment and a second radio network nodeserving the second user equipment. The first radio communications systemhas a first priority in a first part of a shared radio spectrum and thesecond radio communications system has a second priority in the firstpart of the shared radio spectrum, wherein the first priority is higherthan the second priority.

The second user equipment comprises a receiving circuit configured toreceive a signal from the first radio network node, which signal isconfigured to control a transmission of the second user equipment.

Since the second user equipment receives the signal from the first radionetwork node, the transmission of the second user equipment iscontrolled, whereby interference from the second user equipment to thefirst base station is avoided or at least reduced. This results in animproved performance in the communications network.

According to a fifth aspect of embodiments herein, the object isachieved by a method in a first radio network node for controllinginterference between transmissions in a first radio communicationssystem comprising a first user equipment and a first radio network nodeserving the first user equipment, and transmissions in a second radiocommunications system comprising a second user equipment and a secondradio network node serving the second user equipment. The first radiocommunications system has a first priority in a first part of a sharedradio spectrum and the second radio communications system has a secondpriority in the first part of the shared radio spectrum, wherein thefirst priority is higher than the second priority.

The first radio network node transmits a signal to the second userequipment, which signal is configured to control a transmission of thesecond user equipment.

According to a sixth aspect of embodiments herein, the object isachieved by a first radio network node for controlling interferencebetween transmissions in a first radio communications system comprisinga first user equipment and a first radio network node serving the firstuser equipment, and transmissions in a second radio communicationssystem comprising a second user equipment and a second radio networknode serving the second user equipment. The first radio communicationssystem has a first priority in a first part of a shared radio spectrumand the second radio communications system has a second priority in thefirst part of the shared radio spectrum, wherein the first priority ishigher than the second priority.

The first radio network node comprises a transmitting circuit configuredto transmit a signal to the second user equipment, wherein the signal isconfigured to control a transmission of the second user equipment.

Since the first radio network node transmits a signal to the second userequipment, the transmission of the second user equipment is controlled.Thereby, interference from the second user equipment to the first basestation is avoided or at least reduced. This results in an improvedperformance in the communications network.

According to a seventh aspect of embodiments herein, the object isachieved by a method in a second user equipment for controllinginterference between transmissions in a first radio communicationssystem comprising a first user equipment and a first radio network nodeserving the first user equipment, and transmissions in a second radiocommunications system comprising a second user equipment and a secondradio network node serving the second user equipment. The first radiocommunications system has a first priority in a first part of a sharedradio spectrum and the second radio communications system has a secondpriority in the first part of the shared radio spectrum, wherein thefirst priority is higher than the second priority.

The second user equipment receives a signal from the first radio networknode, which signal is configured to inform the second user equipmentthat the first radio network node intends to transmit a downlink signalto the first user equipment at a certain point in time.

Further, based on the signal received from the first radio network node,the second user equipment transmits an uplink signal to the second radionetwork node, which uplink signal controls whether or not the secondradio network node should transmit a downlink signal to the second userequipment.

According to an eight aspect of embodiments herein, the object isachieved by a second user equipment for controlling interference betweentransmissions in a first radio communications system comprising a firstuser equipment and a first radio network node serving the first userequipment, and transmissions in a second radio communications systemcomprising a second user equipment and a second radio network nodeserving the second user equipment. The first radio communications systemhas a first priority in a first part of a shared radio spectrum and thesecond radio communications system has a second priority in the firstpart of the shared radio spectrum, wherein the first priority is higherthan the second priority:

The second user equipment comprises a receiving circuit configured toreceive a signal from the first radio network node, which signal isconfigured to inform the second user equipment that the first radionetwork node intends to transmit a downlink signal at a certain point intime.

Further, the second user equipment comprises a transmitting circuitconfigured to, based on the reception of the signal from the first radionetwork node, transmit an uplink signal to the second radio networknode, which uplink signal controls whether or not the second radionetwork node should perform a downlink transmission to the second userequipment.

Since the second user equipment receives the signal from the first radionetwork node, and since the second user equipment transmits an uplinksignal to the second radio network node, which uplink signal controlswhether or not the second radio network node should perform a downlinktransmission to the second user equipment, the transmission of thesecond radio network node is controlled. Thereby, unnecessarytransmissions from the second base station, creating unnecessaryinterference, is avoided or at least reduced. This results in animproved performance in the communications network.

An advantage of embodiments herein is that the benefits of both alicensed spectrum operation and an unlicensed spectrum operation areachieved. That means that the same available spectrum is made availableto multiple operators, similar to unlicensed spectrum operation, while,at the same time, more controlled interference situations is providedsimilar to conventionally licensed spectrum.

A further advantage of embodiments herein is that the overall availablespectrum is available to each operator similar to unlicensed spectrumoperation.

A yet further advantage of embodiments herein is that a controlledinterference situation similar to licensed spectrum operation isprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in more detail with reference to thefollowing drawings, in which:

FIG. 1 is a schematic block diagram illustrating embodiments of acommunications network;

FIG. 2 is a schematic combined block diagram and signalling schemeillustrating embodiments of a communications network;

FIG. 3 is a schematic combined block diagram and signalling schemeillustrating embodiments of a communications network;

FIG. 4 is a schematic combined block diagram and signalling schemeillustrating embodiments of a communications network;

FIG. 5 is a flowchart depicting embodiments of a method in a first userequipment;

FIG. 6 is a flowchart depicting embodiments of a method in a second userequipment;

FIG. 7 is a flowchart depicting embodiments of a method in a first radionetwork node;

FIG. 8 is a flowchart depicting embodiments of a method in a second userequipment;

FIG. 9 is a schematic block diagram illustrating embodiments of a firstuser equipment;

FIG. 10 is a schematic block diagram illustrating embodiments of asecond user equipment; and

FIG. 11 is a schematic block diagram illustrating embodiments of a firstradio network node.

DETAILED DESCRIPTION

Embodiments herein will be exemplified in the following non-limitingdescription.

Embodiments described herein provide a spectrum-sharing solution thatachieves the benefits of both licensed and unlicensed spectrumoperation. In other words, embodiments herein make the same availablespectrum available to multiple operators, similar to unlicensed spectrumoperation, while, at the same time, provide more controlled interferencesituations similar to conventionally licensed spectrum operation.

FIG. 1 schematically illustrates embodiments of a radio communicationssystem 100. The radio communication system 100 may be a 3GPPcommunications system or a non-3GPP communications system.

The radio communications system 100 comprises a first radiocommunications system 110, which first radio communications system 110may be a 3GPP communications system or a non-3GPP communications system.The first radio communications system 110 comprises a first userequipment 112 and a first radio network node 114 serving the first userequipment 112.

The first user equipment 112 may be e.g. a mobile terminal or a wirelessterminal, a mobile phone, a computer such as e.g. a laptop, a tablet pcsuch as e.g. an iPad™, a Personal Digital Assistant (PDA), or any otherradio network unit capable to communicate over a radio link in acellular communications network. The first user equipment 112 mayfurther be configured for use in both a 3GPP network and in a non-3GPPnetwork.

The first radio network node 114 may be a base station such as an eNB,an eNodeB, Node B or a Home Node B, a Home eNode B, a radio networkcontroller, a base station controller, an access point, a relay node(which may be fixed or movable), a donor node serving a relay, aGSM/EDGE radio base station, a Multi-Standard Radio (MSR) base stationor any other network unit capable to serve the first user equipment 112in the cellular communications system.

Further, the first radio network node 114 provides radio coverage overat least one geographic area 114 a. The at least one geographic area 114a may form a cell. The first user equipment 112 transmits data over aradio interface to the first radio network node 114 in an uplink (UL)transmission and the first radio network node 114 transmits data to thefirst user equipment 112 in a downlink (DL) transmission. A number ofother user equipments, not shown, may also be located within thegeographic area 114 a.

The radio communications system 100 comprises further a second radiocommunications system 120, which second radio communications system 120may be a 3GPP communications system or a non-3GPP communications system.The second radio communications system 120 comprises a second userequipment 122 and a second radio network node 124 serving the seconduser equipment 122.

The second user equipment 122 may be e.g. a mobile terminal or awireless terminal, a mobile phone, a computer such as e.g. a laptop, atablet pc such as e.g. an iPad™, a Personal Digital Assistant (PDA), orany other radio network unit capable to communicate over a radio link ina cellular communications network. The second user equipment 122 mayfurther be configured for use in both a 3GPP network and in a non-3GPPnetwork.

The second radio network node 124 may be a base station such as an eNB,an eNodeB, Node B or a Home Node B, a Home eNode B, a radio networkcontroller, a base station controller, an access point, a relay node(which may be fixed or movable), a donor node serving a relay, aGSM/EDGE radio base station, a Multi-Standard Radio (MSR) base stationor any other network unit capable to serve the second user equipment 122in the cellular communications system.

Further, the second radio network node 124 provides radio coverage overat least one geographic area 124 a. The at least one geographic area 124a may form a cell. The second user equipment 122 transmits data over aradio interface to the second radio network node 124 in an uplink (UL)transmission and the second radio network node 124 transmits data to thesecond user equipment 122 in a downlink (DL) transmission. A number ofother user equipments, not shown, may also be located within thegeographic area 124 a.

FIG. 1 schematically illustrates a general situation addressed byembodiments herein. Within a certain area there are two communicationssystems; the first communications system 110 and the secondcommunications system 120, corresponding to two different operators.However, it should be understood that the number of communicationssystem sharing a certain area may be may be more than two, as may thenumber of operators.

As previously described, each of the first and second communicationssystem 110,120 comprises one or more user equipments 112,122, and one ormore radio network nodes 114,124.

Further, the two communications systems; the first and the secondcommunication systems 110,120, are operating in the same shared spectrumand the aim is to allow for both communications systems 110,120 to beable to use the shared spectrum while avoiding unacceptably highinterference between the two communications systems 110.

It is assumed herein that the first communications system 110 has ahigher priority than the second communications system 120. By higherpriority is meant that the first communications system 110 for examplehas a higher priority in terms of having access to the spectrum ascompared to the second communications system 120. Thus, if there aretransmissions from the first communications system 110 within thespectrum, the second communications system 120 should only use thespectrum in such a way that transmissions from the second communicationssystem 120 do not cause unacceptable interference to transmissions fromthe first communications system 110.

The priorities of the communications systems 110,120 within the sharedradio spectrum are set, e.g. predefined, by the owner or theadministrator of the shared radio spectrum. The priorities may forexample be change over time or between different parts of the sharedradio spectrum, as will be described below. The priority of the firstcommunications system 110 may be signalled from the first radio networknode 114 to the first user equipment 112, and the priority of the secondcommunications system 120 may be signalled from the second radio networknode 124 to the second user equipment 122. Further, the first and secondradio network node 114,124 may have information about the priorities ofother communications systems comprised in the communication system 100.This priority information may also be signalled from the respectiveradio network node 114,124 to the respective user equipment 112,122. Byunacceptably high interference or unacceptable interference, when usedherein, is meant an interference that degrades the communication qualitywithin the communication system having the highest priority such thatthe communication quality within the communication system having thehighest priority is below a pre-defined quality of service level. Thus,an acceptable interference does not degrade the communication qualitywithin the communication system having the highest priority to be belowthe pre-defined quality of service level.

By the term “pre-defined quality of service level” when used in thisdescription is meant a level that is set or configured in advance, e.g.before the operation, wherein it is used, is executed. It should beunderstood that the pre-defined level may be changed, e.g. in dependenceof service quality requirements.

FIG. 2 schematically illustrates a combined block diagram and signallingscheme of embodiments of the communications system 100. As illustratedin FIG. 1, the communications system 100 comprises the firstcommunications system 110, which comprises the first user equipment 112and the first radio network node 114 serving the first user equipment112. The communications system 100 comprises further the secondcommunications system 120, which comprises the second user equipment 122and the second radio network node 124 serving the second user equipment122. The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority. The geographic areas 114 a, 124 a are not shown in FIG.2 for clarity reason.

As schematically illustrated in FIG. 2, a downlink transmission S22 fromthe second radio network node 124 to the second user equipment 122 mayinterfere, by means of an interfering signal S23, a downlinktransmission S24 from the first radio network node 114 to the first userequipment 112. Since the first radio communication system 110 has ahigher priority than the second radio communication system 120, thedownlink transmission S24 from the first radio network node 114 to thefirst user equipment 112 is a prioritized transmission. This isindicated by a thick arrow in FIG. 2. Some embodiments herein providefor the second radio network node 124 to be informed about the potentialinterference situation. This is performed by means of a signal S21transmitted by the first user equipment 112, which signal S21 informsabout the potential interference situation. The signal S21 is indicatedby a dashed arrow in FIG. 2. The second radio network node 124 maytherefore avoid or at least modify some part of the transmission S22,thereby avoiding causing unacceptable interference to thehigher-priority first communications system 110.

A method in the first user equipment 112 relating to this scenario willbe described in more detail below with reference to FIG. 5.

FIG. 3 schematically illustrates a combined block diagram and signallingscheme of embodiments of the communications system 100. As illustratedin FIG. 1, the communications system 100 comprises the firstcommunications system 110, which comprises the first user equipment 112and the first radio network node 114 serving the first user equipment112. The communications system 100 comprises further the secondcommunications system 120, which comprises the second user equipment 122and the second radio network node 124 serving the second user equipment122. The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority. The geographic areas 114 a, 124 a are not shown in FIG.3 for clarity reason.

As schematically illustrated in FIG. 3, an uplink transmission S32 fromthe second user equipment 122 to the second radio network node 124 mayinterfere, by means of an interfering signal S33, an uplink transmissionS34 from the first user equipment 112 to the first radio network node114. Since the first radio communication system 110 has a higherpriority than the second radio communication system 120, the uplinktransmission S34 from the first user equipment 112 to the first radionetwork node 114 is a prioritized transmission. This is indicated by athick arrow in FIG. 3. In such case, embodiments herein provide for thesecond user equipment 122 to be informed, by means of a signal S31transmitted from the first radio network node 114, about this potentialinterference situation. The signal S31 is indicated by a dashed arrow inFIG. 3. Thereby, the second user equipment 122 may avoid or at leastmodify some part of the transmission S32. This may be done regardless ofwhether or not the second user equipment 122 has been scheduled foruplink transmission by the second radio network node 124.

A method in the second user equipment 122 and a method in the firstradio network node 114 relating to this scenario will be described inmore detail below with reference to FIGS. 6 and 7, respectively.

FIG. 4 schematically illustrates a combined block diagram and signallingscheme of embodiments of the communications system 100. As illustratedin FIG. 1, the communications system 100 comprises the firstcommunications system 110, which comprises the first user equipment 112and the first radio network node 114 serving the first user equipment112. The communications system 100 comprises further the secondcommunications system 120, which comprises the second user equipment 122and the second radio network node 124 serving the second user equipment122. The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority. The geographic areas 114 a, 124 a are not shown in FIG.4 for clarity reason.

As schematically illustrated in FIG. 4, a downlink transmission S44 fromthe first radio network node 114 to the first user equipment 122 mayinterfere, by means of an interfering signal S43, a downlinktransmission S42 from the second radio network node 124 to the seconduser equipment 122. Since the first radio communication system 110 has ahigher priority than the second radio communication system 120, thedownlink transmission S44 from the first radio network node 114 to thefirst user equipment 112 is a prioritized transmission. This isindicated by a thick arrow in FIG. 4. In such case, embodiments hereinprovide for the second user equipment 122 to discover this potentialinterference situation, e.g. by receiving a signal S41 from the firstradio network node 114, and inform, by means of a signal S45, the secondradio network node 124 about it. The signal S41 is indicated by a dashedarrow in FIG. 4. The second radio network node 124 may then avoid makingthe transmission S42 that would anyway most likely fail due to severeinterference S43 from the first communications system 110.

A method in the second user equipment 122 relating to this scenario willbe described in more detail below with reference to FIG. 8.

Even if not described in more detail herein, it should be understoodthat a similar interference situation (not shown) may occur in an uplinktransmission from the first user equipment 112 to the first radionetwork node 114. Thus, an uplink transmission from the first userequipment 112 to the first radio network node 114 may interfer an uplinktransmission from the second user equipment 122 to the second radionetwork node 124. In such case, the second radio network node 124 shouldnot schedule an uplink transmission from the second user equipment 122.

A method in a first user equipment 112 for controlling interferencebetween transmissions in the first radio communications system 110 andtransmissions in the second communications system 120 will now bedescribed with reference to FIG. 5, and to the previously describedscenario of FIG. 2 for the schematic illustration of the signalsS21-S24.

As previously mentioned, the first communications system 110 comprisesthe first user equipment 112 and the first radio network node 114serving the first user equipment 112. Further, the second radiocommunications system 120 comprises the second user equipment 122 andthe second radio network node 124 serving the second user equipment 122.The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority.

The actions do not have to be performed in the order stated below, butmay be taken in any suitable order. Further, actions may be combined.Optional actions are indicated by dashed boxes.

Action 601

In order to inform one or more radio network nodes 124 that they shouldobey a signal S21 received from the first user equipment 112, the firstuser equipment 112 may register to the one or more second radio networknodes 124 by performing high level signalling.

By the term “register/registering” when used herein should be understoodto mean that the one or more second radio network nodes 124 receiveinformation that they should listen to and obey a signal S21 receivedfrom the first user equipment 112.

In some embodiments, the first user equipment 112 register to the one ormore radio network nodes 124 by communicating with the second radionetwork node 124 in advance, such as before the first user equipment 112transmits the signal S21.

However, it should be understood that the first user equipment 112 mayregister with the second radio network node 124 via the firstcommunication system 110, whereby the second radio network node 124 maybe informed by the first communication system 110 via backhaulsignalling to listen to and obey possible S21 signalling from the firstuser equipment 112.

Action 502

In some embodiments, in order to determine when to register to a secondradio network node 124, the first user equipment 112 may determine anestimate of a path loss between the first user equipment 112 and thesecond radio network node 124, and an estimate of a path loss betweenthe first user equipment 112 and the first radio network node 114. Aswill be mentioned in Action 503 below, the first user equipment 112 mayregister to the second radio network node 124 based on the determinedpath loss estimates.

In some embodiments, the first user equipment 112 may determine arelative path loss as the estimate of the path loss between the firstuser equipment 112 and the second radio network node 124 relative to theestimate of the path loss between the first user equipment 112 and thefirst radio network node 114.

The first user equipment 112 may determine the path loss as thedifference between the transmit power that a received signal wastransmitted with and the power the received signal had when it wasreceived at the first user equipment 112.

The first user equipment 112 may measure the power of a received signal.Further, information about the transmit power may be comprised in thereceived signal. In some embodiments, information about the transmitpower is signalled separately from the respective radio network node114,124 to the first user equipment 112.

However, in some embodiments, the first user equipment 112 has noknowledge about the transmit power of signals transmitted from the radionetwork nodes 114,124. In such embodiments, the first user equipment 112may assume that the transmit power of signals transmitted from the firstradio network node 114 is the same as the transmit power of signalstransmitted from the second radio network node 124.

In some embodiments, when the first user equipment 112 has no knowledgeabout the transmit power of signals transmitted from the radio networknodes 114,124, the first user equipment 112 may have knowledge about arelationship between the transmit power of signals transmitted from thefirst radio network node 114 and the transmit power of signalstransmitted from the second radio network node 124. For example, thefirst user equipment 112 may know that the first radio network node 114transmits signals with a transmit power that is 10 percent higher thanthe transmit power of signals transmitted from the second radio networknode 124. This may be used when calculating the relative path loss.

Action 503

In some embodiments, the first user equipment 112 registers to thesecond radio network node 124 based on the determined path lossestimates.

For example, the first user equipment 112 may register to the secondradio network node 124 when the determined path loss estimates are belowa respective predefined value.

In some embodiments, the first user equipment 112 registers to thesecond radio network node 124 when the relative path loss is below apredefined value. If the relative path loss is below the predefinedvalue, a transmission S22 from the second radio network node 124 to thesecond user equipment 122 is considered to cause an unacceptableinterference S23 at the first user equipment 112.

It should be understood that in case the relative path loss has beendetermined, the first user equipment 112 registers to the second radionetwork node 124 when the relative path loss is below a predefinedvalue.

The pre-defined value may be a value that has been configured by thefirst radio network node 114 and communicated from the first radionetwork node 114 to the first user equipment 112.

Whether or not the second radio network node 124 should react to thesignal S21 from the first user equipment 112 may depend on the signalstrength by which the signal S21 is received at the second radio networknode 124. For example, the second radio network node 124 should react tothe signal S21 if the received signal power is above a certain thresholdvalue. This is based on an assumption that the stronger the signal S21is received at the second radio network node 124, the smaller is thepath loss between the second radio network node 124 and the first userequipment 112. In this case, the first user equipment 112 sets thetransmit power of the signal S21 depending on the power by which thefirst user equipment 112 receives a downlink signal from the first radionetwork node 114. Essentially, the lower the received power of thedownlink signal from the first radio network node 114, the stronger thetransmit power of the signal S21 in order for the signal S21 to reachthe second radio network node 124. This is described in actions 504 and505 below.

By the term “pre-defined value” when used in this description is meant avalue that is set or configured in advance, e.g. before the operation,wherein it is used, is executed. It should be understood that thepre-defined value may be changed, e.g. in dependence of service qualityrequirements.

Action 504

In some embodiments, the first user equipment 112 receives a downlinksignal S24 from the first base station 114.

Action 505

Upon reception of the downlink signal S24 from the first bases station114 mentioned in action 504 above, the first user equipment 112 may setthe transmit power of a signal S21 to be transmitted to the second basestation 124. As will be described in action 507, the signal S21 isconfigured to control the transmission S22 of the second radio networknode 124 in order to avoid unacceptable interference at the first userequipment 112.

Action 506

In some embodiments, the first user equipment 112 determines an estimateof a path loss between the first user equipment 112 and the second radionetwork node 124. As mentioned under Action 502, the first userequipment 112 may determine the path loss as the difference between thetransmit power of the received signal and a measured power of thereceived signal. Further, as will be described in action 507 below, thevalue of the estimated path loss in relation to a predefined value maycontrol whether or not the first user equipment 112 will transmit thesignal S21 to the second radio network node 124.

Action 507

In order to avoid unacceptable interference at the first user equipment112, the first user equipment 112 transmits the signal S21 to the secondradio network node 124, which second radio network node 124 is toperform a downlink transmission S22 to the second user equipment 122.The signal S21 is configured to control the transmission S22 of thesecond radio network node 124.

In some embodiments, the signal S21 is configured to inform the secondbase station 124 that the downlink transmission S22 will interfere, bymeans of an interfering signal S23, a downlink transmission S24 from thefirst base station 114 to the first user equipment 112.

The signal S21 may be configured to prevent the second radio networknode 124 from performing the downlink transmission S22.

The signal S21 may be configured to control the second radio networknode 124 to transmit only with a limited transmit power. The limitedtransmit power may be a reduced transmit power as compared to the normalmaximum transmit power.

In some embodiments, the signal S21 is configured to control the secondradio network node 124 to perform only downlink control signalling S22.

Further, the signal S21 may further be configured to control thedownlink transmission S22 of the second radio network node 124 for aspecific period of time or for a specific frequency resource.

In some embodiments, the signal S21 is dedicated for the second radionetwork node 124 and the first user equipment 112 transmits the signalS21 on a radio resource dedicated for the second radio network node 124.The dedicated radio resource may comprise a time-domain resource, afrequency-domain resource, a code-domain resource or a combinationthereof. In such embodiments, when the first user equipment 112 wants tocontrol the transmission of a plurality of second radio network nodes124, the first user equipment 112 has to transmit a plurality of S21signals on different resources, one for each second radio network node124.

In some other embodiments, the signal S21 is non-dedicated for thesecond radio network node 124 and valid for one or more other secondradio network nodes. In such embodiments, the first user equipment 112transmits the signal S21 on a radio resource non-dedicated for thesecond radio network node 124. The radio resource may comprise atime-domain resource, a frequency-domain resource, a code-domainresource or a combination thereof. In such embodiments, when the firstuser equipment 112 wants to control the transmission of a plurality ofsecond radio network nodes 124, the first user equipment 112 has totransmit only one S21 signal on one resource.

In some embodiments, the first user equipment 112 may transmit thesignal S21 in a resource dedicated for the first user equipment 112. Thededicated resource may comprise a time-domain resource, afrequency-domain resource, a code-domain resource or a combinationthereof. However, the first user equipment 112 may also transmit thesignal S21 in a resource non-dedicated for the first user equipment 112.The non-dedicated resource, sometimes also referred to as a commonresource, may comprise a time-domain resource, a frequency-domainresource, a code-domain resource or a combination thereof.

When a path loss estimate between the first user equipment 112 and thesecond radio network node 124 has been determined as described in action506 above, the first user equipment 112 transmits the signal S21 to thesecond radio network node 124 when the determined path loss estimate isbelow a predefined value.

In some embodiments, during an on-going transmission session from thefirst radio network node 114 to the first user equipment 112, the firstuser equipment 112 transmits the signal S21 to the second radio networknode 124 based on an expectation to receive a downlink transmission S24from the first radio network node 114 at certain point in time. Since,the transmission session is an on-going transmission session between thefirst user equipment 112 and the first radio network node 114, the firstuser equipment 112 is in active mode and therefore knows that it willreceive the downlink transmission 824 from the first radio network node114 at some point in time. The downlink transmission S24 would beinterfered by a downlink transmission S23 from the second radio networknode 124 at the same point in time.

The transmission of the signal S21 may also, additionally oralternatively, be conditioned on estimates by the first user equipment112 of to what extent it would be interfered by the second radio networknode 124 when it transmits. Such estimation could e.g. be based on thefirst user equipment's 112 estimates of the path loss or some otherrelated measure, to the second radio network node 124. Only if theestimated path loss is below a certain predefined value or if theestimated interference is above a certain predefined value and the firstuser equipment 112 expects that it is to receive the downlinktransmission S24 from the first radio network node 114, the first userequipment 112 will transmit the signal S21.

A method in a second user equipment 122 for controlling interferencebetween transmissions in the first radio communications system 110 andtransmissions in the second communications system 120 will now bedescribed with reference to FIG. 6, and to the previously describedscenario of FIG. 3 for the schematic illustration of the signalsS31-S34.

As previously mentioned, the first communications system 110 comprisesthe first user equipment 112 and the first radio network node 114serving the first user equipment 112. Further, the second radiocommunications system 120 comprises the second user equipment 122 andthe second radio network node 124 serving the second user equipment 122.The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority.

The actions do not have to be performed in the order stated below, butmay be taken in any suitable order. Further, actions may be combined.Optional actions are indicated by dashed boxes.

Action 601

In order to avoid causing interference at the first radio network node114, the second user equipment 122 receives a signal S31 from the firstradio network node 114. The signal S31 is configured to control atransmission S32 of the second user equipment 122, which transmissionS32 may cause interference at the first radio network node 114, by meansof an interfering signal S33 received at the first radio network node114. The signal S31 may be configured to control the transmission S32 ofthe second user equipment 122 independently on whether or not the seconduser equipment 122 has been scheduled for transmission by the secondradio network node 124.

In some embodiments, the signal S31 is further configured to control thesecond user equipment 122 not to perform the transmission S32.

The signal S31 may be configured to control the second user equipment122 to transmit only up to a limited transmit power. The limitedtransmit power may be a reduced transmit power as compared to the normalmaximum transmit power.

The signal S1 may be configured to control the transmission S32 of thesecond user equipment 122 for a specific period of time or for aspecific frequency resource.

In some embodiments, wherein the signal S31 is dedicated for the seconduser equipment 122, the second user equipment 122 receives the signalS31 on a radio resource dedicated for the second user equipment 122.

The dedicated radio resource may comprise a time-domain resource, afrequency-domain resource, a code-domain resource or a combinationthereof.

In some embodiments, wherein the signal S31 is non-dedicated for thesecond user equipment 122 and thus valid for one or more other seconduser equipment 122, the second user equipment 122 receives the signalS31 on a radio resource non-dedicated for the second user equipment 122.

The non-dedicated radio resource may comprise a time-domain resource, afrequency-domain resource, a code-domain resource or a combination.

A method in a first radio network node 114 for controlling interferencebetween transmissions in the first radio communications system 110 andtransmissions in the second communications system 120 will now bedescribed with reference to FIG. 7, and to the previously describedscenario of FIG. 3 for the schematic illustration of the signalsS31-S33.

As previously mentioned, the first communications system 110 comprisesthe first user equipment 112 and the first radio network node 114serving the first user equipment 112. Further, the second radiocommunications system 120 comprises the second user equipment 122 andthe second radio network node 124 serving the second user equipment 122.The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority.

The actions do not have to be performed in the order stated below, butmay be taken in any suitable order. Further, actions may be combined.Optional actions are indicated by dashed boxes.

Action 701

In order to avoid interference at the first radio network node 114, thefirst radio network node 114 transmits a signal S31 to the second userequipment 122. The signal S31 is configured to control a transmissionS32 of the second user equipment 122, which transmission S32 may causeinterference at the first radio network node 114, by means of aninterfering signal S33 received at the first radio network node 114. Thesignal S31 may be configured to control the transmission S32 of thesecond user equipment 122 independently on whether or not the seconduser equipment 122 has been scheduled for transmission by the secondradio network node 124.

In some embodiments, the signal S31 is configured to control the seconduser equipment 122 not to perform the transmission S32.

The signal S31 may be configured to control the second user equipment122 to transmit only up to a limited transmit power. The limitedtransmit power may be a reduced transmit power as compared to the normalmaximum transmit power.

The signal S31 may be configured to control the transmission S32 of thesecond user equipment 122 for a specific period of time or for aspecific frequency resource.

In some embodiments, wherein the signal S31 is dedicated for the seconduser equipment 122, the first radio network node 114 transmits thesignal S31 on a radio resource dedicated for the second user equipment122.

The dedicated radio resource may comprise a time-domain resource, afrequency-domain resource, a code-domain resource or a combinationthereof.

In some embodiments, wherein the signal S31 is non-dedicated for thesecond user equipment 122 and thus valid for one or more other seconduser equipment 122, the first radio network node 114 transmits thesignal S31 on a radio resource non-dedicated for the second userequipment 122.

The non-dedicated radio resource, sometimes also referred to as commonresource, may comprise a time-domain resource, a frequency-domainresource, a code-domain resource or a combination thereof.

A method in a second user equipment 122 for controlling interferencebetween transmissions in the first radio communications system 110 andtransmissions in the second communications system 120 will now bedescribed with reference to FIG. 8, and to the previously describedscenario of FIG. 4 for the schematic illustration of the signalsS41-S45.

As previously mentioned, the first communications system 110 comprisesthe first user equipment 112 and the first radio network node 114serving the first user equipment 112. Further, the second radiocommunications system 120 comprises the second user equipment 122 andthe second radio network node 124 serving the second user equipment 122.The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority.

The actions do not have to be performed in the order stated below, butmay be taken in any suitable order. Further, actions may be combined.Optional actions are indicated by dashed boxes.

Action 801

In order to prevent the second radio network node 124 to transmit asignal S42 to the second user equipment 122 if it is assumed that such atransmission S42 would experience too much interference S43, due totransmission S44 from the first radio network node 114, the second userequipment 122 receives a signal S41 from the first radio network node114. The signal S41 is configured to inform the second user equipment122 that the first radio network node 114 intends to transmit a downlinksignal S44 to the first user equipment 112 at a certain point in time.

In some embodiments, the signal S42 may be seen as an intend-to-transmitsignal that indicates to the second user equipment 122 an intention ofthe first radio network node 114 to transmit at some future timeinstance.

Action 802

The second user equipment 122 may estimate a first path loss between thesecond user equipment 122 and the first radio network node 114. Thefirst path loss may give an indication of how strong interference asignal transmitted from the first radio network node 114 may cause atthe second user equipment 122.

By estimating the first path loss, the second user equipment 122 maydetermine a signal quality of a signal, e.g. an interfering signal S43,transmitted from the first radio network node 114. Thus, the second userequipment 122 may determine the interference, e.g. a level ofinterference, such a signal would cause at the second user equipment122.

The second user equipment 122 may determine the path loss as thedifference between the transmit power that a received signal wastransmitted with and the power the received signal had when it wasreceived at the second user equipment 122.

The second user equipment 122 may measure the power of a receivedsignal. Further, information about the transmit power may be comprisedin the received signal. In some embodiments, information about thetransmit power is signalled separately from the respective radio networknode 114,124 to the second user equipment 122.

However, in some embodiments, the second user equipment 122 has noknowledge about the transmit power of signals transmitted from the radionetwork nodes 114,124. In such embodiments, the second user equipment122 may assume that the transmit power of signals transmitted from thefirst radio network node 114 is the same as the transmit power ofsignals transmitted from the second radio network node 124.

In some embodiments, when the second user equipment 122 has no knowledgeabout the transmit power of signals transmitted from the radio networknodes 114,124, the second user equipment 122 may have knowledge about arelationship between the transmit power of signals transmitted from thefirst radio network node 114 and the transmit power of signalstransmitted from the second radio network node 124. For example, thesecond user equipment 122 may know that the first radio network node 114transmits signals with a transmit power that is 10 percent higher thanthe transmit power of signals transmitted from the second radio networknode 124. This may be used when calculating the relative path loss.

Action 803

In some embodiments, the second user equipment 122 estimates a secondpath loss between the second user equipment 122 and the second radionetwork node 124. The second estimated path loss may give an indicationof how strong a received signal from the second network node 124 may be.By estimating the second path loss, the second user equipment 122 maydetermine a signal quality of a signal S42 transmitted from the secondradio network node 124. Thus, the second user equipment 122 maydetermine how affected such a signal S42 would be of interference causedby an interfering signal S43 transmitted from the first radio networknode 114. For example, if the signal quality of the interfering signalS43 is above a certain service of quality level and the signal qualityof the signal S42 is below a certain quality of service value, thesecond user equipment 122 would not be able to receive the signal S42properly since the signal S42 will be too affected by the interferingsignal S43.

Action 804

The second user equipment 122 may estimate a signal quality for anexpected downlink signal S42 from the second radio network node 124based on the estimated first and second path losses. In other words, thesignal quality may be based on the indication of how good the receptionquality of the signal may be, i.e. the first estimated path loss, andbased on the indication on how strong the received signal may be, i.e.the second estimated path loss. In some embodiments, the signal qualityof the expected downlink signal S42 is calculated as the ratio betweenthe first estimated path loss and the second estimated path loss.

If the signal quality for the expected downlink signal S42 is deemed tobe too low, i.e. to be below a certain service of quality level, thismay be signaled to the second radio network node 124 as an indicationthat the second radio network node 124 should not transmit to the seconduser equipment 122. However, it should be understood that the seconduser equipment 122 may, based on the estimated channel quality, providean indication to the second radio network node 124 that the second radionetwork node 124 may transmit i.e. that the estimated signal quality isabove a certain service of quality level.

In some embodiments, the certain service of quality level is set by theowner or the administrator of the communications system 100. The certainservice of quality level may be dynamically changeable over time independence of e.g. service quality requirements.

Action 805

The second user equipment 122 transmits an uplink signal S45 to thesecond radio network node 124. The uplink signal S45 is transmittedbased on the received signal S41 and controls whether or not the secondradio network node 124 should transmit a downlink signal S42 to thesecond user equipment 122.

In some embodiments, the second user equipment 122 transmits the uplinksignal S45 based on an estimated signal quality of the signal S41. Theestimated signal quality may be estimated by the second user equipment122.

To perform the method actions in the first user equipment 112 describedabove in relation to FIG. 5 for controlling interference betweentransmissions in the first radio communications system 110 andtransmissions in the second communications system 120, the first userequipment 112 comprises the following arrangement depicted in FIG. 9.

As previously mentioned, the first communications system 110 comprisesthe first user equipment 112 and the first radio network node 114serving the first user equipment 112. Further, the second radiocommunications system 120 comprises the second user equipment 122 andthe second radio network node 124 serving the second user equipment 122.The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority.

The first user equipment 112 comprises a transmitting circuit 901configured to transmit a signal S21 to a second radio network node 124that is to perform a downlink transmission S22 to the second userequipment 122. The signal S21 is configured to control the transmissionS22,S23 of the second radio network node 124. In other words, the signalS21 may be configured to control the downlink transmission S22 from thesecond radio network node 124 to the second user equipment 122 in orderto avoid an interfering signal S23 at the first user equipment 112.

In some embodiments, the signal S21 is configured to prevent the secondradio network node 124 from performing the downlink transmission S22.

The signal S21 may be configured to control the second radio networknode 124 to transmit only with a limited transmit power. The limitedtransmit power may be a reduced transmit power as compared to the normalmaximum transmit power.

The signal S21 may be configured to control the second radio networknode 124 to perform only downlink control signaling S22.

In some embodiments, the signal S21 is configured to control thedownlink transmission S22 of the second radio network node 124 for aspecific period of time or for a specific frequency resource.

In some embodiments, wherein the signal S21 is dedicated for the secondradio network node 124, the transmitting circuit 901 is configured totransmit the signal S21 on a radio resource dedicated for the secondradio network node 124. The dedicated radio resource may comprise atime-domain resource, a frequency-domain resource, a code-domainresource or a combination thereof.

In some embodiments, wherein the signal S21 is non-dedicated for thesecond radio network node 124, and thus valid for one or more othersecond radio network nodes, the transmitting circuit 901 is configuredtransmit the signal S21 on a radio resource non-dedicated for the secondradio network node 124. The non-dedicated radio resource, sometimes alsoreferred to as common resource, may comprise a time-domain resource, afrequency-domain resource, a code-domain resource or a combinationthereof.

The transmitting circuit 901 may further be configured to transmit thesignal S21 in a resource dedicated for the first user equipment 112. Thededicated resource may comprise a time-domain resource, afrequency-domain resource, a code-domain resource or a combinationthereof.

In some embodiments, the transmitting circuit 901 may further beconfigured to transmit the signal S21 in a resource non-dedicated forthe first user equipment 112. The non-dedicated resource, sometimes alsoreferred to as common resource, comprises a time-domain resource, afrequency-domain resource, a code-domain resource or a combinationthereof.

During an on-going transmission session from the first radio networknode 114, the transmitting circuit 901 may be configured to transmit thesignal S21 to the second radio network node 124 based on an expectationto receive a downlink transmission S24 from the first radio network node114 at certain point in time. The downlink transmission S24 would beinterfered by a downlink transmission S23 from the second radio networknode 124 at the same point in time.

The transmitting circuit 901 may further be configured to transmit thesignal S21 to the second radio network node 124 when an estimated pathloss is below a predefined value. The estimated path loss may bedetermined by a determining circuit 903 which will be described below.

The first user equipment 112 may further comprise a registering circuit902 configured to register the first user equipment 112 to the one ormore second radio network node 124 by performing high level signaling.

In some embodiments, the registering circuit 902 is configured toregister to the one or more radio network nodes 124 by communicatingwith the second radio network node in advance, such as before the firstuser equipment 112 transmits the signal S21.

However, it should be understood that the first user equipment 112 mayregister to the second radio network node 124 via the firstcommunication system 110, whereby the second radio network node 124 maybe informed by the first communication system 110 via backhaulsignalling to listen to and obey possible S21 signalling from certainfirst user equipments 112.

The registering circuit 902 may be configured to register the first userequipment 112 to the second radio network node 124 when a relative pathloss is below a predefined value. The relative path loss may bedetermined by a determining circuit 903 which will be described below.

In some embodiments, the registering circuit 902 may be configured toregister to the second radio network node 124 based on determined pathloss estimates. The path loss estimates may be determined by thedetermining circuit 903 described below.

In some embodiments, the first user equipment 112 comprises further adetermining circuit 903 configured to determine a relative path loss asthe estimate path loss between the first user equipment 112 and thesecond radio network node 124 relative to the estimated path lossbetween the first user equipment 112 and the first radio network node114.

The determining circuit 903 may determine an estimate of the path lossbetween the first user equipment 112 and the second radio network node124, and an estimate of the path loss between the first user equipment112 and the first radio network node 114. As is mentioned above, theregistering circuit 902 may register to the second radio network node124 when at least one of the determined path loss estimates is below arespective predefined value.

The determining circuit 903 may determine the path loss as thedifference between the transmit power that a received signal wastransmitted with and the power the received signal had when it wasreceived at the first user equipment 112.

The determining circuit 903 may measure the power of a received signal.Further, information about the transmit power may be comprised in thereceived signal. In some embodiments, information about the transmitpower is signalled separately from the respective radio network node114,124 to the first user equipment 112.

However, in some embodiments, the determining circuit 903 has noknowledge about the transmit power of signals transmitted from the radionetwork nodes 114,124. In such embodiments, the determining circuit 903may assume that the transmit power of signals transmitted from the firstradio network node 114 is the same as the transmit power of signalstransmitted from the second radio network node 124.

In some embodiments, when the determining circuit 903 has no knowledgeabout the transmit power of signals transmitted from the radio networknodes 114,124, the determining circuit 903 may have knowledge about arelationship between the transmit power of signals transmitted from thefirst radio network node 114 and the transmit power of signalstransmitted from the second radio network node 124. For example, thedetermining circuit 903 may know that the first radio network node 114transmits signals with a transmit power that is 10 percent higher thanthe transmit power of signals transmitted from the second radio networknode 124. This may be used when calculating the relative path loss.

The first user equipment 112 may further comprise a receiving circuit904 configured to receive signals from the first and second radionetwork nodes 114,124.

Embodiments herein for controlling interference between transmissions inthe first radio communications system 110 and transmissions in thesecond communications system 120 may be implemented through one or moreprocessors, such as a processing circuit 905 in the first user equipment112 depicted in FIG. 9, together with computer program code forperforming the functions and/or method actions of embodiments herein.

It should be understood that one or more of the circuits comprised inthe first user equipment 112 described above may be integrated with eachother to form an integrated circuit.

The first user equipment 112 may further comprise a memory 906. Thememory may comprise one or more memory units and may be used to storefor example data such as thresholds, predefined or preset information,etc.

To perform the method actions in the second user equipment 122 describedabove for controlling interference between transmissions in the firstradio communications system 110 and transmissions in the secondcommunications system 120, the second user equipment 122 comprises thefollowing arrangement depicted in FIG. 10.

As previously mentioned, the first communications system 110 comprisesthe first user equipment 112 and the first radio network node 114serving the first user equipment 112. Further, the second radiocommunications system 120 comprises the second user equipment 122 andthe second radio network node 124 serving the second user equipment 122.The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority.

In some embodiments, e.g. embodiments relating to FIG. 3, the seconduser equipment 122 comprises a receiving circuit 1001 configured toreceive a signal S31 from the first radio network node 114. The signalS31 is configured to control a transmission S32 of the second userequipment 122.

In some embodiments, the signal S31 is configured to control the seconduser equipment 122 not to perform the transmission S32.

The signal S31 may be configured to control the second user equipment122 to transmit only up to a limited transmit power. The limitedtransmit power may be a reduced transmit power as compared to the normalmaximum transmit power.

The signal S31 may further be configured to control the transmission ofthe second user equipment 122 for a specific period of time or for aspecific frequency resource.

In some embodiments, wherein the signal S31 is dedicated for the seconduser equipment 122 the receiving circuit 1101 is further configured toreceive the signal on a radio resource dedicated for the second userequipment 122. The dedicated radio resource may comprise a time-domainresource, a frequency-domain resource, a code-domain resource or acombination thereof.

In some other embodiments, wherein the signal S31 is non-dedicated forthe second user equipment 122, and thus valid for one or more othersecond user equipment 122, the receiving circuit 1101 is furtherconfigured to receive the signal on a radio resource non-dedicated forthe second user equipment 122. The non-dedicated radio resource maycomprise a time-domain resource, a frequency-domain resource, acode-domain resource or a combination thereof.

In some embodiments, e.g. embodiments relating to FIG. 4, the receivingcircuit 1001 configured to receive a signal S41 from the first radionetwork node 114. The signal S41 is configured to inform the second userequipment 122 that the first radio network node 114 intends to transmita downlink signal S44 to the first user equipment 112 at a certain pointin time.

In some embodiments, the second user equipment 122 further comprises adetermining circuit 1002. The determining circuit 1002 may be configuredto determine a first estimate of a path loss between the second userequipment 122 and the first radio network node 114. The determiningcircuit 1002 is further configured to determine a second estimate of apath loss between the second user equipment 122 and the second radionetwork node 124. Based on the first and second estimates of path loss,the determining circuit 1002 is configured to determine a signal qualityfor an expected signal from the second radio network node.

The determining circuit 1002 may determine the path loss as thedifference between the transmit power that a received signal wastransmitted with and the power the received signal had when it wasreceived at the second user equipment 122.

The determining circuit 1002 may measure the power of a received signal.Further, information about the transmit power may be comprised in thereceived signal. In some embodiments, information about the transmitpower is signalled separately from the respective radio network node114,124 to the second user equipment 122.

However, in some embodiments, the determining circuit 1002 has noknowledge about the transmit power of signals transmitted from the radionetwork nodes 114,124. In such embodiments, the determining circuit 1002may assume that the transmit power of signals transmitted from the firstradio network node 114 is the same as the transmit power of signalstransmitted from the second radio network node 124.

In some embodiments, when the determining circuit 1002 has no knowledgeabout the transmit power of signals transmitted from the radio networknodes 114,124, the determining circuit 1002 may have knowledge about arelationship between the transmit power of signals transmitted from thefirst radio network node 114 and the transmit power of signalstransmitted from the second radio network node 124. For example, thedetermining circuit 1002 may know that the first radio network node 114transmits signals with a transmit power that is 10 percent higher thanthe transmit power of signals transmitted from the second radio networknode 124. This may be used when calculating the relative path loss.

The second user equipment 122 may further comprise a transmittingcircuit 1003 configured to transmit an uplink signal S45 to the secondradio network node 124. The transmitting circuit 1003 may be configuredto transmit the uplink signal S45 based on the signal S41 received fromthe first radio network node 114. In some embodiments, the transmittingcircuit 1003 is configured to transmit the signal S45 based on anexpected signal quality of the signal S41. The expected signal qualitymay be determined by the second user equipment 122, e.g. by means of thedetermining circuit 1002. The expected signal quality of the signal S41may be determined based on an estimated path loss between the firstradio network node 114 and the second user equipment 122.

The uplink signal S45 is configured to control, whether or not thesecond radio network node 124 should perform a downlink transmission S42to the second user equipment 122.

Embodiments herein for controlling interference between transmissions inthe first radio communications system 110 and transmissions in thesecond communications system 120 may be implemented through one or moreprocessors, such as a processing circuit 1004 in the second userequipment 122 depicted in FIG. 10, together with computer program codefor performing the functions and/or method actions of embodimentsherein.

It should be understood that one or more of the circuits comprised inthe second user equipment 122 described above may be integrated witheach other to form an integrated circuit.

The second user equipment 122 may further comprise a memory 1005. Thememory may comprise one or more memory units and may be used to storefor example data such as thresholds, predefined or preset information,etc.

To perform the method actions in the first radio network node 114described above for controlling interference between transmissions inthe first radio communications system 110 and transmissions in thesecond communications system 120, the second user equipment 122comprises the following arrangement depicted in FIG. 11.

As previously mentioned, the first communications system 110 comprisesthe first user equipment 112 and the first radio network node 114serving the first user equipment 112. Further, the second radiocommunications system 120 comprises the second user equipment 122 andthe second radio network node 124 serving the second user equipment 122.The first radio communications system 110 has a first priority in afirst part of a shared radio spectrum and the second radiocommunications system 120 has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority.

The first radio network node 114 comprises a transmitting circuit 1101configured to transmit a signal S31 to the second user equipment 122.The signal S31 is configured to control a transmission S32 of the seconduser equipment 122.

The signal S31 may further be configured to control the second userequipment 122 not to perform the transmission S32.

The signal S31 may be configured to control the second user equipment122 to transmit only up to a limited transmit power. The limitedtransmit power may be a reduced transmit power as compared to the normalmaximum transmit power.

In some embodiments, the signal S31 is further configured to control thetransmission of the second user equipment 122 for a specific period oftime or for a specific frequency resource.

In some embodiments, wherein the signal S31 is dedicated for the seconduser equipment 122, the transmitting circuit 1101 may further beconfigured to transmit the signal S31 on a radio resource dedicated forthe second user equipment 122. The dedicated radio resource may comprisea time-domain resource, a frequency-domain resource, a code-domainresource or a combination thereof.

In some other embodiments, wherein the signal S31 is non-dedicated forthe second user equipment 122 and valid for one or more other seconduser equipment 122, the transmitting circuit 1101 may further beconfigured to transmit the signal S31 on a radio resource non-dedicatedfor the second user equipment 122. The non-dedicated radio resource maycomprise a time-domain resource, a frequency-domain resource, acode-domain resource or a combination thereof.

The first radio network node 114 may further comprise a receivingcircuit 1102 configured to receive signals from the first and seconduser equipments, 112,122.

Embodiments herein for controlling interference between transmissions inthe first radio communications system 110 and transmissions in thesecond communications system 120 may be implemented through one or moreprocessors, such as a processing circuit 1103 in the first radio networknode 114 depicted in FIG. 11, together with computer program code forperforming the functions and/or method actions of embodiments herein.

It should be understood that one or more of the circuits comprised inthe first radio network node 114 described above may be integrated witheach other to form an integrated circuit.

The first radio network node 114 may further comprise a memory 1104. Thememory may comprise one or more memory units and may be used to storefor example data such as thresholds, predefined or preset information,etc.

The following is applicable to any suitable embodiment described above.In some embodiments described herein, non-equality between thecommunications systems 110,120 has been assumed. More specifically, ithas been assumed that the first communications system 110 is a primarysystem with a higher priority, and that the second communications system120 is a secondary system with a lower priority. As previouslymentioned, the priorities of the communications systems 110,120 are setby the owner or the administrator of the shared radio spectrum.

Different means may be used to compensate for the inequality between thecommunications systems 110,120, i.e. to ensure that, at least on a morelong-term basis, the first and second communications systems 110,120have the same overall access to the spectrum resource.

For example, the spectrum may be divided into two parts, e.g. part A andpart B. One of the communications systems 110,120 may then be a primarysystem in spectrum part A and a secondary system in spectrum part B,while the other one of the communications systems 110,120 may be asecondary system in spectrum part A and primary system in spectrum partB. As understood by those skilled in the art, the above describedactions and features should then be performed on a per-spectrum-partbasis.

As another example, the priority of the two communications systems110,120 may be varied over time so that the role of being primary andsecondary system is varying over time according to some pre-definedrule.

Further, embodiments herein have been described with reference to twocommunications systems 110,120. However, embodiments may comprise morethan two communications systems of different priorities. In general,embodiments herein may comprise N communications systems with prioritiesprio-1, prio-2, . . . prio-N, wherein prio-1 corresponds to the highestpriority and prio-N corresponds to the lowest priority. The embodimentsdescribed herein would then correspond to N=2, with the firstcommunications system 110 having a priority corresponding to prio-1 andthe second communications system 120 having a priority corresponding toprio-2.

In case of more than two communications systems, a communications systemwith priority X may behave as a secondary communications system inrelation to all communications systems having a priority Y, whichpriority Y is higher than the priority X. Thus, all communicationssystems having the priority Y will behave as a primary communicationssystem in relation the communications system with priority X.

Correspondingly, the communications system with priority X may behave asa primary communications system versus all communications systems havinga priority Z, which priority Z is less than the priority X. Thecommunications systems having the priority Z will behave as secondarycommunications system in relation to the communications system withpriority X.

Thus, the fairness between two communications systems as described inembodiments herein may be extended to the case of N communicationssystems.

Further, in case of spectrum division as described above, the overallavailable spectrum may be split into M parts where the differentcommunications systems may be assigned different priorities in thedifferent spectrum parts.

Furthermore, in case of time variation as described above, thepriorities of each communications system may be changed over timeaccording to some pre-defined rule.

Although the description above contains many specifics, they should notbe construed as limiting but as merely providing illustrations of somepresently preferred embodiments. The technology fully encompasses otherembodiments which may become apparent to those skilled in the art.Reference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.” Allstructural and functional equivalents to the elements of theabove-described embodiments that are known to those of ordinary skill inthe art are expressly incorporated herein by reference and are intendedto be encompassed hereby. Moreover, it is not necessary for a device ormethod to address each and every problem sought to be solved by thedescribed technology for it to be encompassed hereby.

When using the word “comprise” or “comprising” it shall be interpretedas non-limiting, in the meaning of consist at least of.

When using the word action/actions it shall be interpreted broadly andnot to imply that the actions have to be carried out in the ordermentioned. Instead, the actions may be carried out in any suitable orderother than the order mentioned. Further, some action/actions may beoptional.

Further, the dotted boxes and dotted arrows in the drawingsschematically illustrate optional features and actions of embodimentsherein.

The embodiments herein are not limited to the above described examples.Various alternatives, modifications and equivalents may be used.Therefore, the above examples should not be taken as limiting the scopeof the invention, which is defined by the appending claims.

1. A method in a first user equipment for controlling interferencebetween transmissions in a first radio communications system comprisingthe first user equipment and a first radio network node serving thefirst user equipment, and transmissions in a second radio communicationssystem comprising a second user equipment and a second radio networknode serving the second user equipment, wherein the first radiocommunications system has a first priority in a first part of a sharedradio spectrum and the second radio communications system has a secondpriority in the first part of the shared radio spectrum, wherein thefirst priority is higher than the second priority, wherein the methodcomprises: transmitting a signal to a second radio network node, whichsecond radio network node is to perform a downlink transmission to thesecond user equipment, which signal is configured to control thetransmission of the second radio network node, whereby interference inthe first radio communications system caused by transmissions from thesecond radio communications system is controlled, and wherebytransmissions in the first radio communication system is prioritized. 2.The method of claim 1, wherein the signal is configured to prevent thesecond radio network node from performing the downlink transmission. 3.The method of claim 1, wherein the signal is configured to control thesecond radio network node to perform only downlink control signaling. 4.The method of claim 1, wherein the signal further is configured tocontrol the downlink transmission of the second radio network node for aspecific period of time or for a specific frequency resource.
 5. Themethod of claim 1, wherein the signal is dedicated for the second radionetwork node and wherein the transmitting of the signal furthercomprises: transmitting the signal on a radio resource dedicated for thesecond radio network node, wherein the radio resource comprises atime-domain resource, a frequency-domain resource, a code-domainresource or a combination thereof.
 6. The method of claim 1, wherein thesignal is non-dedicated for the second radio network node and valid forone or more other second radio network nodes, and wherein thetransmitting of the signal further comprises: transmitting the signal ona radio resource non-dedicated for the second radio network node,wherein the radio resource comprises a time-domain resource, afrequency-domain resource, a code-domain resource or a combinationthereof.
 7. The method of claim 1, further comprising: determining anestimate of a path loss between the first user equipment and the secondradio network node and an estimate of a path loss between the first userequipment and the first radio network node; and registering to thesecond radio network node when at least one the estimated path lossesare below a respective predefined value.
 8. The method of claim 1,further comprising: determining a relative path loss as the path lossbetween the first user equipment and the second radio network noderelative to the path loss between the first user equipment and the firstradio network node; and registering to the second radio network nodewhen the relative path loss is below a pre-defined value.
 9. The methodof claim 1, wherein the transmitting of the signal further comprises:transmitting the signal in a resource dedicated to the first userequipment, wherein the dedicated resource comprises a time-domainresource, a frequency-domain resource, a code-domain resource or acombination thereof.
 10. The method of claim 1, wherein the transmittingof the signal further comprises: transmitting the signal in a resourcenon-dedicated to the first user equipment, wherein the non-dedicatedresource comprises a time-domain resource, a frequency-domain resource,a code-domain resource or a combination thereof.
 11. The method of claim1, further comprising: determining an estimate of a path loss betweenthe first user equipment and the second radio network node; and whereinthe transmitting of the signal comprises transmitting the signal to thesecond radio network node when the determined path loss estimate isbelow a pre-defined value.
 12. The method of claim 1, wherein thetransmitting of the signal further comprises: during an on-goingtransmission session from the first radio network node, transmitting thesignal to the second radio network node based on an expectation toreceive a downlink transmission from the first radio network node atcertain point in time, which downlink transmission would be interferedby a downlink transmission from the second radio network node at thesame point in time.
 13. A method in a second user equipment forcontrolling interference between transmissions in a first radiocommunications system comprising the first user equipment and a firstradio network node serving the first user equipment, and transmissionsin a second radio communications system comprising a second userequipment and a second radio network node serving the second userequipment, wherein the first radio communications system has a firstpriority in a first part of a shared radio spectrum and the second radiocommunications system has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority, and wherein the method comprises: receiving a signalfrom the first radio network node, which signal is configured to controla transmission of the second user equipment, whereby interference in thefirst radio communications system caused by transmissions from thesecond radio communications system is controlled, and wherebytransmissions in the first radio communication system is prioritized.14. The method of claim 13, wherein the signal further is configured tocontrol the second user equipment not to perform the transmission. 15.The method of claim 13, wherein the signal further is configured tocontrol the transmission of the second user equipment for a specificperiod of time or for a specific frequency resource.
 16. The method ofclaim 13, wherein the signal is dedicated for the second user equipmentand wherein the receiving of the signal further comprises: receiving thesignal on a radio resource dedicated for the second user equipment,wherein the radio resource comprises a time-domain resource, afrequency-domain resource, a code-domain resource or a combinationthereof.
 17. The method of claim 13, wherein the signal is non-dedicatedfor the second user equipment and valid for one or more other seconduser equipment, and wherein the receiving of the signal furthercomprises: receiving the signal on a radio resource non-dedicated forthe second user equipment, wherein the radio resource comprises atime-domain resource, a frequency-domain resource, a code-domainresource or a combination thereof.
 18. A method in a first radio networknode for controlling interference between transmissions in a first radiocommunications system comprising the first user equipment and a firstradio network node serving the first user equipment, and transmissionsin a second radio communications system comprising a second userequipment and a second radio network node serving the second userequipment, wherein the first radio communications system has a firstpriority in a first part of a shared radio spectrum and the second radiocommunications system has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority, and wherein the method comprises: transmitting a signalto the second user equipment, which signal is configured to control atransmission of the second user equipment, whereby interference in thefirst radio communications system caused by transmissions from thesecond radio communications system is controlled, and wherebytransmissions in the first radio communication system is prioritized.19. The method of claim 18, wherein the signal further is configured tocontrol the second user equipment not to perform the transmission. 20.The method of claim 18, wherein the signal further is configured tocontrol the transmission of the second user equipment for a specificperiod of time or for a specific frequency resource.
 21. The method ofclaim 18, wherein the signal is dedicated for the second user equipmentand wherein the transmitting of the signal further comprises:transmitting the signal on a radio resource dedicated for the seconduser equipment, wherein the radio resource comprises a time-domainresource, a frequency-domain resource, a code-domain resource or acombination thereof.
 22. The method of claim 19, wherein the signal isnon-dedicated for the second user equipment and valid for one or moreother second user equipment, and wherein the transmitting of the signalfurther comprises: transmitting the signal on a radio resourcenon-dedicated for the second user equipment, wherein the radio resourcecomprises a time-domain resource, a frequency-domain resource, acode-domain resource or a combination thereof.
 23. A method in a seconduser equipment for controlling interference between transmissions in afirst radio communications system comprising the first user equipmentand a first radio network node serving the first user equipment, andtransmissions in a second radio communications system comprising asecond user equipment and a second radio network node serving the seconduser equipment, wherein the first radio communications system has afirst priority in a first part of a shared radio spectrum and the secondradio communications system has a second priority in the first part ofthe shared radio spectrum, wherein the first priority is higher than thesecond priority, and wherein the method comprises: receiving a signalfrom the first radio network node, which signal is configured to informthe second user equipment that the first radio network node intends totransmit a downlink signal to the first user equipment at a certainpoint in time; and based on the received signal, transmitting an uplinksignal to the second radio network node, which uplink signal controlswhether or not the second radio network node should transmit thedownlink signal to the second user equipment, whereby interference inthe first radio communications system caused by transmissions from thesecond radio communications system is controlled, and wherebytransmissions in the first radio communication system is prioritized.24. The method of claim 23, wherein the transmitting of the uplinksignal further comprises: transmitting the uplink signal based on anexpected signal quality of the signal, which expected signal quality isdetermined by the second user equipment based on an estimate of a pathloss between the second radio network node and the second userequipment.
 25. The method of claim 23, further comprising: estimating afirst path loss between the second user equipment and the first radionetwork node; estimating a second path loss between the second userequipment and the second radio network node; and estimating a signalquality for an expected downlink signal from the second radio networknode based on the estimated first and second path losses.
 26. A firstuser equipment for controlling interference between transmissions in afirst radio communications system comprising the first user equipmentand a first radio network node serving the first user equipment, andtransmissions in a second radio communications system comprising asecond user equipment and a second radio network node serving the seconduser equipment, wherein the first radio communications system has afirst priority in a first part of a shared radio spectrum and the secondradio communications system has a second priority in the first part ofthe shared radio spectrum, wherein the first priority is higher than thesecond priority, wherein the first user equipment comprises: atransmitting circuit configured to transmit a signal to a second radionetwork node, which second radio network node is to perform a downlinktransmission to the second user equipment, which signal is configured tocontrol the transmission of the second radio network node, wherebyinterference in the first radio communications system caused bytransmissions from the second radio communications system is controlled,and whereby transmissions in the first radio communication system isprioritized.
 27. The first user equipment of claim 26, wherein thesignal is configured to prevent the second radio network node fromperforming the downlink transmission.
 28. The first user equipment ofclaim 26, wherein the signal is configured to control the second radionetwork node to perform only downlink control signaling.
 29. The firstuser equipment of claim 26, wherein the signal further is configured tocontrol the downlink transmission of the second radio network node for aspecific period of time or for a specific frequency resource.
 30. Thefirst user equipment of claim 26, wherein the signal is dedicated forthe second radio network node and wherein the transmitting circuitfurther is configured to: transmit the signal on a radio resourcededicated for the second radio network node, wherein the radio resourcecomprises a time-domain resource, a frequency-domain resource, acode-domain resource or a combination thereof.
 31. The first userequipment of claim 26, wherein the signal is non-dedicated for thesecond radio network node and valid for one or more other second radionetwork nodes, and wherein the transmitting circuit further isconfigured to: transmit the signal on a radio resource non-dedicated forthe second radio network node; wherein the radio resource comprises atime-domain resource, a frequency-domain resource, a code-domainresource or a combination thereof.
 32. The first user equipment of claim26, further comprising: a determining circuit configured to determine arelative path loss as the path loss between the first user equipment andthe second radio network node relative to the path gain between thefirst user equipment and the first radio network node, and wherein theregistering circuit further is configured to register the first userequipment to the second radio network node when the relative path lossis below a pre-defined value.
 33. The first user equipment of claim 26,wherein: the determining circuit is configured to determine an estimateof a path loss between the first user equipment and the second radionetwork node and an estimate of a path loss between the first userequipment and the first radio network node, and wherein: the registeringcircuit is configured to register to the second radio network node whenat least one of the estimated path losses is below a respectivepredefined value.
 34. The first user equipment of claim 26, wherein thetransmitting circuit further is configured to transmit the signal in aresource dedicated to the first user equipment, wherein the dedicatedresource comprises a time-domain resource, a frequency-domain resource,a code-domain resource or a combination thereof.
 35. The first userequipment of claim 26, wherein the transmitting circuit further isconfigured to transmit the signal in a resource non-dedicated to thefirst user equipment, wherein the non-dedicated resource comprises atime-domain resource, a frequency-domain resource, a code-domainresource or a combination thereof.
 36. The first user equipment of claim26, further comprising: a determining circuit configured to determine anestimate of a path loss between the first user equipment and the secondradio network node; and wherein the transmitting circuit further isconfigured to transmit the signal to the second radio network node whenthe estimated path loss is below a pre-defined value.
 37. The first userequipment of claim 26, wherein the transmitting circuit further isconfigured to: during an on-going transmission session from the firstradio network node, transmit the signal to the second radio network nodebased on a expectation to receive a downlink transmission from the firstradio network node at certain point in time, which downlink transmissionwould be interfered by a downlink transmission from the second radionetwork node at the same point in time.
 38. A second user equipment forcontrolling interference between transmissions in a first radiocommunications system comprising a first user equipment and a firstradio network node serving the first user equipment, and transmissionsin a second radio communications system comprising a second userequipment and a second radio network node serving the second userequipment, wherein the first radio communications system has a firstpriority in a first part of a shared radio spectrum and the second radiocommunications system has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority, and wherein the second user equipment comprises: areceiving circuit configured to receive a signal from the first radionetwork node, which signal is configured to control a transmission ofthe second user equipment, whereby interference in the first radiocommunications system caused by transmissions from the second radiocommunications system is controlled, and whereby transmissions in thefirst radio communication system is prioritized.
 39. The second userequipment of claim 38, wherein the signal is configured to control thesecond user equipment not to perform the transmission.
 40. The seconduser equipment of claim 38, wherein the signal further is configured tocontrol the transmission of the second user equipment for a specificperiod of time or for a specific frequency resource.
 41. The second userequipment of claim 38, wherein the signal is dedicated for the seconduser equipment and wherein the receiving circuit further is configuredto: receive the signal on a radio resource dedicated for the second userequipment, wherein the radio resource comprises a time-domain resource,a frequency-domain resource, a code-domain resource or a combinationthereof.
 42. The second user equipment of claim 38, wherein the signalis non-dedicated for the second user equipment and valid for one or moreother second user equipment, and wherein the receiving circuit furtheris configured to: receive the signal on a radio resource non-dedicatedfor the second user equipment, wherein the radio resource comprises atime-domain resource, a frequency-domain resource, a code-domainresource or a combination thereof.
 43. A first radio network node forcontrolling interference between transmissions in a first radiocommunications system comprising a first user equipment and a firstradio network node serving the first user equipment, and transmissionsin a second radio communications system comprising a second userequipment and a second radio network node serving the second userequipment, wherein the first radio communications system has a firstpriority in a first part of a shared radio spectrum and the second radiocommunications system has a second priority in the first part of theshared radio spectrum, wherein the first priority is higher than thesecond priority, and wherein the first radio network node comprises: atransmitting circuit configured to transmit a signal to the second userequipment, wherein the signal is configured to control a transmission ofthe second user equipment, whereby interference in the first radiocommunications system caused by transmissions from the second radiocommunications system is controlled, and whereby transmissions in thefirst radio communication system is prioritized.
 44. The first radionetwork node of claim 43, wherein the signal further is configured tocontrol the second user equipment not to perform the transmission. 45.The first radio network node of claim 43, wherein the signal further isconfigured to control the transmission of the second user equipment fora specific period of time or for a specific frequency resource.
 46. Thefirst radio network node of claim 43, wherein the signal is dedicatedfor the second user equipment and wherein the transmitting circuitfurther is configured to: transmit the signal on a radio resourcededicated for the second user equipment, wherein the radio resourcecomprises a time-domain resource, a frequency-domain resource, acode-domain resource or a combination thereof.
 47. The first radionetwork node of claim 43, wherein the signal is non-dedicated for thesecond user equipment and valid for one or more other second userequipment, and wherein the transmitting circuit further is configuredto: transmit the signal on a radio resource non-dedicated for the seconduser equipment, wherein the radio resource comprises a time-domainresource, a frequency-domain resource, a code-domain resource or acombination thereof.
 48. A second user equipment for controllinginterference between transmissions in a first radio communicationssystem comprising a first user equipment and a first radio network nodeserving the first user equipment, and transmissions in a second radiocommunications system comprising a second user equipment and a secondradio network node serving the second user equipment, wherein the firstradio communications system has a first priority in a first part of ashared radio spectrum and the second radio communications system has asecond priority in the first part of the shared radio spectrum, whereinthe first priority is higher than the second priority, and wherein thesecond user equipment comprises: a receiving circuit configured toreceive a signal from the first radio network node, which signal isconfigured to inform the second user equipment that the first radionetwork node intends to transmit a downlink signal to the first userequipment at a certain point in time; and a transmitting circuitconfigured to, based on the received signal, transmit an uplink signalto the second radio network node, which uplink signal controls whetheror not the second radio network node should perform a downlinktransmission to the second user equipment whereby interference in thefirst radio communications system caused by transmissions from thesecond radio communications system is controlled, and wherebytransmissions in the first radio communication system is prioritized.49. The second user equipment of claim 48, wherein the transmittingcircuit further is configured to transmit the uplink signal based on anexpected signal quality of the signal, which expected signal quality isdetermined by the second user equipment based on an estimate of a pathloss between the second radio network node and the second userequipment.
 50. The second user equipment of claim 48, furthercomprising: a determining circuit configured to determine: a firstestimate of a path loss between the second user equipment and the firstradio network node; a second estimate of a path loss between the seconduser equipment and the second radio network node; and an estimatedsignal quality for an expected downlink signal from the second radionetwork node based on the first and second estimates of path loss.